LH (Luteinizing Hormone)

Overview

Luteinizing hormone (LH) measures a glycoprotein hormone secreted by gonadotroph cells in the anterior pituitary gland under GnRH stimulation. LH stimulates ovulation and corpus luteum formation in females, and testosterone production by Leydig cells in males. Elevated levels indicate primary gonadal failure, menopause, or PCOS; low levels suggest secondary hypogonadism or pituitary dysfunction. LH testing is clinically essential for evaluating infertility, puberty disorders, and menstrual irregularities.

Clinical Use Cases

  • Diagnosing primary versus secondary hypogonadism.
  • Evaluating amenorrhea, anovulation, and infertility.
  • Assessing precocious puberty or delayed puberty.
  • Monitoring ovulation induction and menopause transition.

Specimen Types

  • Serum.
  • Plasma (heparin or EDTA).

Measurement Methods

  • Chemiluminescent immunometric assay (most common).
  • Electrochemiluminescent immunoassay.
  • Time-resolved fluoroimmunoassay.

Test Preparation and Influencing Factors

  • Time collection to early follicular phase (days 2-5) for baseline female levels.
  • Pregnancy suppresses LH secretion.
  • Estrogen therapy, clomiphene, or GnRH agonists/antagonists alter levels.
  • Stress, anorexia nervosa, or extreme exercise transiently increase LH.

Synonyms

  • Luteinizing hormone.
  • Interstitial cell-stimulating hormone (ICSH, male-specific term).
  • Lutropin.

Further Reading